1. Field of the Invention
The present invention relates to a cooler for an electronic unit that is used for cooling a central processing unit (CPU) in a notebook-sized personal computer, and an electronic unit with the cooler, and more particularly to an electronic-unit cooler and an electronic with the cooler in which the cooling performance has been enhanced.
2. Related Art
In notebook-sized personal computers, the amount of heat generated in a CPU increases, as the CPU is operated at a higher speed. For this reason, there has been a demand for cooling of the CPU, and a wide variety of coolers for an electronic unit have been proposed.
The CPU cooler disclosed in Published Unexamined Patent Application No. 2000-323880 utilizes a heat pipe. The heat pipe transfers the heat of a CPU to the entire keyboard and discharges the heat to the outside through the entire keyboard. The heat pipe also transfers the heat to a cooling fan and discharges the heat by forced cooling.
In the CPU cooler disclosed in Published Unexamined Patent Application No. 2000-13065, a CPU and a fan are horizontally disposed adjacent to each other. A heat sink covers the top surfaces of the CPU and the fan, and a heat pipe extends along the side portion of the heat sink. The heat of the CPU is transferred toward the fan through the heat sink and the heat pipe. In this manner, the heat is discharged by forced cooling.
In the CPU cooler disclosed in Published Unexamined Patent Application No. 2000-277964, one portion of a heat sink covers a CPU, and a fan disposing space is provided inside another portion of the heat sink. A heat pipe is attached to the heat sink and extends from the CPU to the air exhaust portion of the fan disposing space and is cooled by a cooling wind within the air exhaust port
In the aforementioned CPU of Published Unexamined Patent Application No. 2000-323880, the cooling performance is insufficient, because only the heat pipe transfers the heat of the CPU toward the fan.
In the aforementioned CPU of Published Unexamined Patent Application No. 2000-13065, the heat pipe is curved and extended at right angles along the side portion of the heat sink and transfers heat from the central portion of the heat sink to the radially outer portion through the heat sink. Because of this, the cooling performances of the heat pipe and the heat sink are not high as a whole.
In the aforementioned CPU of Published Unexamined Patent Application No. 2000-277964, cooling of the heat pipe is performed at the outlet port. Because of this, the heat pipe is long in length and the refraction becomes greater. As a result, the heat transfer performance is reduced. In addition, the heat pipe is of a round pipe type and therefore requires a large cooling plate to assure a radiation surface.
It is an object of the present invention to enhance the performances of the heat sink and the heat pipe, in an electronic-unit cooler for discharging the heat of a heat generating body by forced air cooling.
Another object of the invention is to provide an electronic unit equipped with a heat sink and a heat pipe having enhanced performance.
In accordance with a first embodiment of the present invention, there is provided a cooler for an electronic unit, including:
a heat sink having (a) a first portion which contacts with a heat generating body directly or through material which efficiently conducts heat, and (b) a second portion defining at least a portion of a fan disposing face;
a fan disposed in the fan disposing space; and
a heat pipe mounted on the heat sink (a) in contact with the heat generating body directly or through the material at the first portion and (b) exposed to the fan disposing space at the second portion.
The aforementioned material includes, for example, grease and/or a high heat-conductive metal member described later. The heat generating body is, for example, a semiconductor device. The semiconductor device includes a semiconductor chip (e.g., a CPU chip) and a semiconductor package that houses the semiconductor chip at least partially in the interior thereof. The electronic unit is, for example, a notebook-sized personal computer, a portable electronic unit, etc. The heat sink is constructed, for example, of an aluminum die casting or a copper die casting. The aluminum die casting is inferior in heat conductivity to the copper die casting, but superior in weight reduction to the copper die casting.
Within the heat pipe, the interior liquid is evaporated by the heat of the heat generating body and cools the heat generating body. The vapor is cooled at the portion, on the side of the heat sink, of the heat pipe by the fan cooling air introduced to the interior surface of the heat sink. The vapor is liquefied and returned toward the heat generating body. The heat sink transfers the heat from the heat generating body, toward the fan disposing space and is cooled in the fan disposing space by the cooling wind caused by the fan.
In a conventional electronic-unit cooler, the heat pipe is mounted on the top surface, that is, the surface opposite to the heat generating body and the fan. However, in the present invention, the heat pipe is exposed to the heat generating body side and the fan disposing space side. Therefore, the absorption of heat from the heat generating body by the heat pipe, and radiation in the fan disposing space, are efficiently performed. This enhances the performance of the electronic-unit cooler significantly.
Further according to the present invention, the fan has a plurality of blades which rotate with a vertical direction of the heat sink as its axis of rotation so that air introduced in the vertical direction is discharged in a radial direction as a horizontal direction. The fan and the heat generating body are disposed side by side in a horizontal direction of the heat sink. Also, the first and second portions are continuous to each other and spread substantially horizontally above the heat generating body and the fan. Furthermore, the heat pipe extends substantially horizontally along the bottom surface of the first and second portions.
In the notebook-sized personal computer, for example, there is a demand for weight reduction and thinning of the main body. In the fan, because of the rotating blades, the dimension in the rotation direction dimension is much smaller than the radial dimension. Therefore, the rotation axis of the rotating blades is reduced in the up-and-down direction. As a result, the thickness of an electronic unit that is mounted in the electronic-unit cooler can be suppressed. The first and second portions of the heat sink spread horizontally, and transfer the heat of the heat generating body to the fan disposing space, while suppressing the height of the electronic-unit cooler. The heat pipe also extends horizontally. The horizontal structure of the heat pipe with no step portion smoothens both the movement of the vapor within the heat pipe from the heat generating body toward the fan disposing space, and the return of liquid from the fan disposing space toward the heat generating body. Thus, the heat pipe is capable of greatly enhancing its performance by extending horizontally along the first and second bottom surfaces
According to an electronic-unit cooler of a third aspect of the present invention, the second portion has a top surface lower than the top surface of the first portion. Also, the lower top surface has an inlet port communicating with the fan disposing space and also reaches at least one side surface of the heat sink.
In the notebook-sized personal computer, for instance, the thickness of the main body in which an electronic-unit cooler is mounted is small, and the gap between the top wall of the housing of the main body and the top surface of the heat sink is small. If a lower top surface area opening to at least one side surface of the heat sink is formed on the top surface side of the heat sink, and an upper inlet port is formed in the lower top surface area, an air flow passage with a predetermined vertical dimension is assured between the lower top surface area and the top wall of the housing. With this, the air is introduced into the fan disposing space through the upper inlet port without difficulty.
According to an electronic-unit cooler of a fourth aspect of the present invention, the bottom surface, on the side of the first portion, of the heat sink is covered with a high heat-conductive metal member comprising a material whose heat conductivity coefficient is greater than that of the heat sink. In addition, the high heat-conductive metal member forms a fan-disposing-space bottom surface which defines the fan disposing space in cooperation with the second portion.
In the case where the material of the heat sink is, for example, aluminum, material constituting a high heat-conductive metal member and also greater in heat conductivity than the material of the heat sink is, for example, copper. The high heat-conductive metal member is typically a plate metal member.
There are cases where the heat pipe is dried out because of high temperature and stops its function, depending on the heat pipe type. The high heat-conductive metal member can suppress the transfer of heat from the heat generating body to the heat pipe suitably and prevent the heat pipe from drying out, because it is interposed between the heat pipe and the heat generating body. The high heat-conductive metal member forms the fan disposing space in cooperation with the second portion of the heat sink. Therefore, part of the heat of the heat generating body is transferred to the fan disposing space through the high heat-conductive metal member and is cooled in the fan disposing space by the cooling wind produced by the fan.
According to an electronic-unit cooler of a fifth aspect of the present invention, a direction in which the first and second portions are continuous to each other is defined as a first horizontal direction and a horizontal direction perpendicular to the first horizontal direction is defined as a second horizontal direction. With this definition, the fan disposing space has a portion which projects from the fan in the second horizontal direction. The heat pipe extends to the projecting portion.
The bottom surface of the second portion requires a predetermined area in order for the heat pipe to assure a portion that is exposed into the fan disposing space. If the size of the horizontal section of the fan disposing space is made equal to the size of the fan, it will become difficult to assure an installation place for the fan-disposing-space bottom surface portion of the heat pipe, particularly when there is an upper inlet port. If the fan disposing space is equipped with a portion projecting in the radial direction of the fan, the fan-disposing-space bottom surface portion of the heat pipe can be disposed, while avoiding the problem of disposition.
According to an electronic-unit cooler of a sixth aspect of the present invention, the heat pipe is formed into a flat shape in which a horizontal direction perpendicular to an extending direction thereof is a width direction.
The heat absorbing area and radiation area of the heat pipe are increased by adoption of the flat heat pipe. As a result, the heat adsorption performance of the heat pipe from the heat generating body and the radiation performance of the heat pipe in the fan disposing space are enhanced.
According to an electronic-unit cooler of a seventh aspect of the present invention, the heat pipe extends linearly.
As a result of the addition of the projecting portion to the fan disposing space, the heat pipe can extend linearly, while assuring the upper inlet port. In addition, in the heat pipe in the form of a straight line, circulation of vapor and liquid is smooth and therefore the performance of the heat pipe is enhanced.
According to an electronic-unit cooler of an eighth aspect of the present invention, the fan disposing space has an exhaust port at its side portion opposite to the heat generating body through the fan. In addition, the exhaust port has dimensions so that at least a portion of the fan within the fan disposing space is exposed to the exhaust port and that at least a portion of the projecting portion is exposed to the exhaust port.
The air that has cooled the heat pipe and the heat sink is discharged from the exhaust port to the outside of the electronic-unit cooler. Preferably, the housing of the electronic-unit cooler has an air hole corresponding to the exhaust port of the electronic-unit cooler, and the cooling wind is discharged outside the housing through the air hole. Since the exhaust port faces both the fan in the fan disposing space and the projecting portion, the inlet air introduced by the fan cools the heat pipe and heat sink within the fan disposing space and then is discharged effectively from the exhaust port, compared with the structure where the exhaust port faces only the fan.
According to an electronic-unit cooler of a ninth aspect of the present invention, the fan-disposing-space bottom surface of the high heat-conductive metal member has a lower inlet port which communicates with the fan disposing space, right under the fan.
The top side and bottom side of the fan disposing space are defined by the second portion of the heat sink and the fan-disposing-space bottom surface portion of the high heat-conductive metal member, respectively. With this, the second portion of the heat sink and the fan-disposing-space bottom surface portion of the high heat-conductive metal member assure sufficient areas within the fan disposing space, respectively. As a result, the radiation efficiency in the fan disposing space is enhanced.
According to an electronic-unit cooler of a tenth aspect of the present invention, the high heat-conductive metal member has a covering portion which spreads horizontally to cover the first portion, the fan-disposing-space bottom surface portion spreading horizontally at a position lower than the covering portion, and a hanging portion which extends vertically to connect the upper covering portion and the lower fan-disposing-space bottom surface portion together. In addition, the hanging portion defines a side portion, on the side of the heat generating body, of the fan disposing space.
The high heat-conductive metal member is equipped integrally with the heat-generating-body side portion, the fan-disposing-space bottom surface portion, and the hanging portion, and is joined to the heat sink. Therefore, satisfactory cooling performance in the fan disposing space is guaranteed, while satisfactory assembly performance of the electronic-unit cooler is being assured. Because the high heat-conductive metal member also defines the fan disposing space at the hanging portion, the cooling effect of the high heat-conductive metal member in the fan disposing space is increased.
In an electronic unit of an eleventh aspect of the present invention, the electronic-unit cooler is housed in the housing of the electric unit. The housing is provided with a first air-passing portion through which air is passed from outside the housing to inside the housing by an air inhaling force produced with the fan, and a second air-passing portion which faces the exhaust port of the fan disposing space so that exhaust from the fan disposing space is passed from inside the housing to outside the housing.
It is preferable that the first air passing portion of the housing be located in a portion of the housing which faces the inlet port through which air is introduced into the fan disposing space. However, the present invention is not limited to this arrangement. In the case where the electronic unit is a notebook-sized personal computer, the first and second air passing portions are formed in the side wall of the housing of the main body. The air heated to a high temperature because of the heat exchange, within the fan disposing space, between the heat sink and the heat pipe is discharged from the exhaust port of the electronic-unit cooler to the outside of the housing though the second air passing portion of the housing facing the exhaust port immediately. As a result, the heated air is preented from remaining within the housing.